During which growth phase does the metaphysis primarily function?

The metaphysis primarily functions during the development of long bones, which is when significant growth and change occur. This region is located between the epiphysis and the diaphysis and is critical during the phases of bone growth.

During development, particularly in childhood and adolescence, the growth plate at the metaphysis (known as the epiphyseal plate) is where longitudinal bone growth occurs. Chondrocytes in this area proliferate and then undergo ossification, contributing to the lengthening of long bones. The metaphysis is highly active during these growth phases, making it the primary area of interest regarding growth and development of bones.

In contrast, during adulthood, the growth plates have typically closed, and the activity in the metaphysis is significantly reduced, focusing more on bone maintenance and remodeling rather than growth. Therefore, the choice referring to the development of long bones accurately captures the essence of the metaphysis's primary function during growth phases.